Abby L.
asked 05/24/13What are the answers to -4+sin(x)=-8+sqrt2/2
I need to know how to find the two answers between 0 and 2 pi. I need the answers in degrees, not radians. there should be two answers
2 Answers By Expert Tutors
Inactive Tutor answered 05/24/13
sin x = (e^ix – e^-ix)/2i
Let sin x = -4 + sqrt2/2 = k = (e^ix – e^-ix)/2i
2ik = (e^ix – e^-ix)
(e^ix – e^-ix) –2ik = 0
e^2ix – 2ike^ix –1 = 0
Let u = e^ix
u^2 – 2iku – 1 = 0, u = (2ik ± (((-2ik)^2 – 4(1)(-1))^(1/2))/2
(-2.586i ± 1.64)/2
u= e^ix ≈ -.4735i, -2.113i
e^ix = -.4735i
ix = ln(-.4735i)
ix = ln(.4735) - (pi)/2
x = -i ln(.4735) – (pi)/2
x = -i(-.748) + (pi)/2
x = -1.57 + .748i
|x| = 1.739, Θ = arctan (.748/-1.57) = 154.5° OR 334.5º
AND
e^ix = -2.113i
ix = ln (-2.113i)
ix = ln (2.113) – ipi/2
x = -i ln (2.113) + (pi)/2
x = -1.57 - .748i
|x| = 1.739, Θ = 25.5° OR 205.5°
Inactive Tutor answered 05/24/13
l sin(x) l ≤ 1 ---> -1 ≤ sin(x) ≤ 1
sin (x) = -4 + (√2)/2 ---> sin(x) ≈ - 3.3 < - 1 , sin(x) is not exist there
~~~~~~~~~~
[0, 360o]
sin x = (√2)/2 ----> x1 = 45o and x2 = 135o
Still looking for help? Get the right answer, fast.
Get a free answer to a quick problem.
Most questions answered within 4 hours.
OR
Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.
Inactive Tutor
Hi Abby. You have to understand the order of operations! There is huge difference between -4 + sin(x) = -8 + v2/2 and
-4 + sin(x) = (-8 + v2) / 2 !!!!!!!
The answer for first one is empty set of numbers, and for another one:
sin(x) = -4 + v2/2 + 4
sin(x) = v2/2 ---> x1 = 45o and x2 = 135o on the segment [0, 2pi].
05/24/13